Abstract
A pellet containing Chlormadinone acetate (CMA; 20mg) was subcutaneously implanted in queens during a year for estrous control, and the concentration of sex steroid hormones in circulation was measured by radioimmnnoassay before and after the removal of CMA pellet. No estrous signs were seen in 29 (96.7%) of 30 treated queens. During the CMA implantation, estradiol-17β remained at a lower level in all cases, sometimes showing a little higher levels, suggesting the development of small follicles. Progesterone remained at lower levels of less than 1ng/ml. The estrus returned at 113 to 172 days (141.8 days on average) after the removal of CMA pellet and 4 queens had some kittens after normal gestation period.
